The present invention relates to copolymers of hydrophobic and hydrophilic blocks, and a method for their preparation.
U.S. Pat. No. 4,581,429, Solomon et al., Apr. 8, 1986, discloses a process for free radical polymerization to produce relatively short chain length homopolymers and copolymers, including block and graft copolymers. The initiator is a compound of the general formula ##STR1## Polymers prepared include methyl acrylate/styrene diblock and styrene/methyl acrylate graft copolymers.
U.S. Pat. No. 5,530,079, Veregin et al., Jun. 25, 1996, discloses a polymerization process comprising heating a mixture of a free radical initiator, a stable free radical agent, at least one polymerizable monomer compound, and optionally a solvent. Among the suitable monomers are carboxylic acid or acrylic monomers, esters, amides, etc. Solvents may be selected from aliphatic alcohols, glycols, ethers, glycol ethers, pyrrolidines, . . . amides, carboxylic acids and salts thereof, etc.
U.S. Pat. No. 3,189,663, Nozakie, Jun. 15, 1965, discloses block copolymers prepared from polymers of certain unsaturated acids. One segment is made up of polymerized ethylenically unsaturated carboxylic acids, anhydrides, esters, or amides. A second segment is made up of dissimilar members of the aforementioned group, esters of unsaturated alcohols and saturated carboxylic acids, alkenes, alkadienes, vinyl halides, vinylidene halides, ethylenically unsaturated nitrites, alkenyl-substituted aromatic hydrocarbons, alkenyl-substituted halo-hydrocarbons, and alkenyl ethers. Polymers having solubility in both water and oil may be obtained by the disclosed process. A preformed polymer of e.g. ethylenically unsaturated carboxylic acids, anhydride thereof, their esters, and amides is mixed with any of the above-mentioned monomers, including, e.g., styrene. The reaction is generally accomplished in a liquid medium such as water, organic solvents or diluents, such as benzene, cyclohexane, xylene, hexane, diheptyl ether and the like.
U.S. Pat. No. 5,401,804, Georges et al., Mar. 28, 1995, discloses a free radical polymerization process, involving heating a mixture of a free radical initiator, a stable free radical agent, and at least one polymerizable monomer. The stable free radical agent can be 2,2,6,6-tetramethyl-1-piperidinyloxy. An organic sulfonic or organic carboxylic acid can be added to increase the rate of formation of the resin.